US president's campaign team, Moscow and WikiLeaks accused of conspiring to influence the 2016 presidential election.

The Democratic Party in the United States has filed a lawsuit alleging that top officials from Donald Trump's presidential campaign, Russia and WikiLeaks conspired to influence the Republican's White House bid in his favour.

The civil complaint filed on Friday accused that Moscow informed Trump's campaign that it had conducted a cyberattack on the Democratic National Committee (DNC), leading to the release of information damaging to the party's presidential nominee, Hillary Clinton.

The lawsuit alleged that Trump's campaign "gleefully welcomed Russia's help" in the 2016 elections and accused it of being a "racketeering enterprise" that worked in tandem with Moscow.

It also involved WikiLeaks and its founder Julian Assange, saying that they gave Trump team officials "advanced knowledge" they were publishing the information.

"During the 2016 presidential campaign, Russia launched an all-out assault on our democracy and it found a willing and active partner in Donald Trump's campaign," said Tom Perez, DNC chairman.

"This constituted an act of unprecedented treachery."

In response, Trump's campaign said later on Friday that the lawsuit was "completely without merit and will be dismissed in due time."

"This frivolous lawsuit is a last-ditch effort to substantiate the baseless Russian collusion allegations by a nearly-bankrupt Democratic Party still trying to counter the will of the people in the 2016 presidential election," a statement issued by Donald J. Trump for President Inc. said.

Trump has repeatedly denied his campaign colluded with Russia, and Moscow has rejected accusations of meddling in the election.

Trump's circle

Defendants in the suit, which was filed in federal court in New York, include three people who have been indicted as a result of Special Counsel Robert Mueller's investigation of alleged Russian meddling: former campaign chairman Paul Manafort, his associate Rick Gates and former campaign aide George Papadopoulos.

Also named as defendants were Donald Trump Jr., Trump associate Roger Stone and Trump's son-in-law, Jared Kushner, as well as Assange.

'On the record'

Four US intelligence agencies reported last year that Russia sponsored the hacking of Democratic Party groups and other actions during the 2016 campaign. Part of the effort was to benefit Trump over Clinton, the agencies said.

The DNC blames Russia for breaches of its computer systems in 2015 and the first half of 2016.

Hackers disseminated internal communications of party officials as the Democratic nominating convention began and WikiLeaks released thousands of emails, some of which were embarrassing for the Clinton campaign and were intended to stoke conflicts among the party's supporters.

Most of the accusations appeared to be based on news reports and publicly available legal documents and offered little new information about alleged collusion with Moscow.